The present invention relates to an apparatus for producing a monocrystal. It more particularly applies to producing monocrystals which can be used as scintillators and more specifically to the production of BaF.sub.2 barium fluoride monocrystals.
Monocrystal production processes are known, the most frequently used being the BRIDGMAN process. In this case, the material to be crystallized is placed in a crucible, which is displaced in a small temperature gradient from a high temperature zone to a low temperature zone. The smallness of the temperature gradient makes it indispensable to previously purify the material, which is generally carried out by the method known as "zone fusion". According to this method, only part of an ingot of the material to be purified is heated, thus forming a thin fusion layer and said layer is then moved from one end of the ingot to the other, the impurities contained in this ingot then being displaced towards one end thereof. This operation has to be repeated a number of times to obtain a very pure material. Moreover, the use of a very abrupt temperature gradient causes the ingot to break up into several pieces, which are unstable as a result of their small size. The BRIDGMAN process is then applied thereto in order to obtain a monocrystal of an appropriate size.
The procedure associating the zone fusion method and the BRIDGMAN process suffers from disadvantages. The procedure is long and complex and requires several manipulations of the material to be crystallized, which increases the risks of pollution thereof, which must obviously be prevented, particularly in the case of crystals for use in the production of scintillators.